diffusion and osmosis experiments

how to investigate diffusion in a non-living organism

make up some agar jelly with phenolphthalein and dilute sodium hydroxide = making jelly pink

put some dilute hydrochloric acid in a beaker

cut few cubes from jelly and put them in beaker of acid

leave the cubes for a while

they will eventually turn colorless as the acid diffuses into the agar jelly

how does phenolphthalein work when investigating diffusion in agar jelly

hydrochloric acid neutralizes sodium hydroxide

when neutralized, pink turns colorless

how to investigate osmosis in a living system

cut up potato into identical cylinders

put different sugar solutions into a beaker

measure lengths of cylinders

then leave it in each beakers for half an hour

take them out, pat them dry

measure their lengths again

how does the lengths change in potato cylinders

if water is drawn in by osmosis, their lengths will be longer = pure water

if water is drawn out, their lengths will be shorter = concentrated sugar solution

how to investigate osmosis in non-living systems

fix a Visking tube over the end of a thistle funnel

put some sugar solution down the glass tube into the thistle funnel

put the thistle funnel into a beaker of pure water

measure where the sugar solution comes up to on the glass tube

leave apparatus overnight

measure again

water should be drawn through the Visking tubing by osmosis

this will force the solution up the glass tube